Decentralised control for parallel inverters connected to the power grid is developed using differential flatness
theory and the derivative-free nonlinear Kalman filter. It is proven that the model of the inverters, is a differentially flat
one. This means that all its state variables and the control inputs can be written as differential functions of a single
algebraic variable which is the flat output. By exploiting differential flatness properties it is shown that the multiple
inverters model can be transformed into a set of local inverter models which are decoupled and linearized. For each
local inverter the design of a state feedback controller becomes possible. Such a controller processes
measurements not only coming from the individual inverter but also coming from other inverters which are
connected to the grid. Moreover, to estimate the non-measurable state variables of each local inverter, the
derivative-free nonlinear Kalman filter is used. Furthermore, by redesigning the aforementioned filter as a
disturbance observer it becomes also possible to estimate and compensate for disturbance terms that affect each
local inverter.

Decentralised control for parallel inverters connected to the power grid is developed using differential flatness
theory and the derivative-free nonlinear Kalman filter. It is proven that the model of the inverters, is a differentially flat
one. This means that all its state variables and the control inputs can be written as differential functions of a single
algebraic variable which is the flat output. By exploiting differential flatness properties it is shown that the multiple
inverters model can be transformed into a set of local inverter models which are decoupled and linearized. For each
local inverter the design of a state feedback controller becomes possible. Such a controller processes
measurements not only coming from the individual inverter but also coming from other inverters which are
connected to the grid. Moreover, to estimate the non-measurable state variables of each local inverter, the
derivative-free nonlinear Kalman filter is used. Furthermore, by redesigning the aforementioned filter as a
disturbance observer it becomes also possible to estimate and compensate for disturbance terms that affect each
local inverter.